1. Field of the Invention
The present invention relates to a flexible printed circuit board which has a metal foil layer formed only on one side of an insulating layer.
2. Description of the Related Art
Various electronic apparatuses employ a flexible printed circuit board (hereinafter also simply referred to as an “FPC”) on which circuits are formed. The configuration of a commonly used double-sided FPC is shown in cross section in FIGS. 2A and 2B.
In FIG. 2A, an FPC 51 has a metal foil layer 54 formed on both sides of an insulating layer 52 via an adhesive layer 53. The FPC 51 includes through holes 55 which are partially formed to provide electrical conduction between the metal foil layers 54 provided on both the sides.
FIG. 2B shows the FPC 51 which is bent with electronic components mounted thereon. Drive ICs 56a and 56b are mounted on the metal foil layers 54 on both the sides, respectively, and the through holes 55 provide electrical conduction between these drive ICs 56a and 56b. 
Inventive examples, which were developed to provide improved convenience to the FPC, are disclosed in Unexamined Japanese Patent Publications Nos. Hei 11-195850 and Hei 4-356996.
An FPC disclosed in Unexamined Japanese Patent Publication No. Hei 11-195850, or a single FPC which includes a double-sided FPC portion and a single-sided FPC portion, is configured such that the single-sided FPC portion is bent to overlap another single-sided FPC portion to make a bent portion of this overlapped portion. The bent portion being formed of a single-sided FPC portion reflects a creative idea to provide an improved bending property.
On the other hand, an FPC disclosed in Unexamined Japanese Patent Publication No. Hei 4-356996 or a double-sided FPC is configured such that a single-sided FPC having a base film coated with an adhesive is provided with holes by machining and affixed with a strip of conductor. The FPC is then subjected to etching for forming a conductor pattern. The FPC is thus provided with an electrically conductive pattern thereon and then cut at the holes, thereby forming terminal portions. This FPC is intended to provide terminal portions at high density and improve process time and costs.
However, so long as a double-sided FPC is employed, a conventional FPC, which is provided on both sides thereof with a metal foil layer, cannot be dispensed with a through hole for providing conduction between the metal foils on both the sides. The through hole thus formed will require to be plated for electrical continuity along the inner wall thereof, thereby causing an increase in the number of processing steps.